Bio-oil upgrading through catalytic vapor cracking removes oxygen from the bio-oil in the forms of CO2, H2O or CO without using external hydrogen. The reactions take place at temperatures of 330-600°C and atmospheric pressure. Solid acid catalysts such as aluminosilicates and zeolite are used for the bio-oil cracking (Park et al. 2011). Atmospheric pressure reaction without the need of external hydrogen makes this process economically attractive. The higher aromatic content in the product results in better fuel quality as compared to the hydrodeoxygenation process. However, catalysts deactivate at a faster rate and H/C ratio of product is lower as compared to those of hydrodeoxygenation products (Graca et al. 2009; Hew et al. 2010; Mortensen et al. 2011). Reaction of cracking can be summarized in the following equation with respect to carbon of bio-oil (Mortensen et al. 2011).

CH14O04^0.9 CH2 + 0.1 CO2 + 0.2 H2O (2)

Where CH14O04 and CH2 represent bio-oil and hydrocarbon product, respectively.